A novel technique for the measurement of disruption in high-pressure homogenization: Studies on E. coli containing recombinant inclusion bodies

The high-pressure homogenization of Escherichia coli, strain JM101, containing inclusion bodies of recombinant porcine somatotropin was investigated. A novel technique employing an analytical disc centrifuge was used to monitor the disruption. This a direct technique which measures cell disintegration rather than soluble protein release. The technique is particularly suited to measurements where the disruption approaches 100%. The disk centrifuge provides a size distribution of the homogenate, and furnishes evidence for the preferential disruption of larger cells. For E. coli containing inclusion bodies, and increase in the cell feed concentration from 145 g/L (wet weight) to 330 g/L resulted is poorer homogenization. Poorer disruption was also obtained by lowering the feed temperature from 20 degrees C to 5 degrees C. Only slight variations in performance were obtained by increasing the feed pH from 7.5 to 9.0 or by storing the feed at 4 degrees C for 24 h prior to disruption. Comparison with uninduced E. coli strain JM101, showed that the disruption obtained is higher for bacteria containing a recombinant inclusion body.     

Concepts of occlusion: Australian evidence

Longitudinal studies of aboriginal children over a 20-year period have drawn attention to the wide variation in morphological features of the dentition and the way in which occlusal relationships develop. This paper summarizes some important determinants of optimal occlusal development, namely, tooth size relationships within and between dentitions, the patterns of alveolar growth, and tooth migrations during the transition from primary to permanent teeth and the nature of growth changes in the dental arches. Dental occlusion constantly changes throughout life in response to changing functional requirements. Observations limited to cross-sectional material provide an incomplete, and sometimes misleading, concept of dental occlusion and masticatory function.     

Cranial morphology and adaptations in Eocene Adapidae. II. The Cambridge skull of Adapis parisiensis

One of the most complete skulls of the early primate Adapis parisiensis is in the collection of the Department of Zoology, Cambridge University. This exceptionally well-preserved male skull, from Quercy in southern France, is important in showing relatively small orbits that are highly convergent, a distinct ethmoid component in the medial orbital wall, very small infraorbital foramina, a well-preserved auditory region with the stapedial canal about twice the diameter of the canal for the promontory artery, and a well-preserved braincase 8.8 cm³ in endocranial volume. The frontal lobe of the brain in the Cambridge skull described here is less expanded than that reported previously in a British Museum skull. The average body weight of Adapis parisiensis is estimated to have been about 2.0 kg, and that of Adapis magnus is estimated to have been about 8.4 to 9.0 kg. The encephalization quotient (EQ) of Adapis parisiensis is estimated to have been 0.45, which is well below the range found in modern prosimians. There is some indication that the size of the foramen magnum has increased with increasing brain size during primate evolution. Adapis parisiensis appears to have been a medium-sized, visually oriented, diurnal, sexually dimorphic arboreal folivore.     

The Benzodiazepine/GABA Receptor Complex: Molecular Size in Brain Synaptic Membranes and in Solution

Abstract: The molecular size of the benzodiazepine (BZ) receptor in the synaptic membrane of brain cortex (bovine or rat) was determined by an improved version of the radiation inactivation method to be 220,000. An identical size was found simultaneously for the associated γ-aminobutyric acid (GABA) receptor and for the component binding β-carboline esters. It is proposed that all three activities reside in a single protein or protein complex in the membrane. The size in solution, after extraction into Triton X-100 medium from exhaustively washed membranes, was estimated by sedimentation constant (9.4S) and by gel filtration (∼230,000 apparent MW), again with the BZ and GABA binding activities behaving identically. This size applies to the component that undergoes photoaffinity labelling by [³H]flunitrazepam in the membrane, and contains a 51,000 M_r polypeptide as the BZ-binding subunit. It is concluded that a protein complex or oligomer of 200,000–220,000 MW carries a class of BZ-binding sites and an associated class of GABA_A sites.     

The relationship between the size of mitochondria and the intensity of light that they scatter in different energetic states

The intensity of light scattered at 90° to the incident beam and the effective hydrodynamic radii of mitochondria incubated under a variety of conditions have been measured. Addition of high concentrations of uncouplers to respiring mitochondria resulted in a decrease in scatter which was not due to swelling. Addition of valinomycin to mitochondria depleted of substrate in K⁺-free medium produced an increase in scatter that was not due to shrinking. It is concluded that changes in the intensity of scattered light are not reliable indices of changes of volume of mitochondria, and that changes in conformation with changes in metabolic state dominate changes in light scatter. A molecular mechanism for the effect of metabolic state upon the scattered intensity is suggested.     

The condensed tannins of pasture legume species

Condensed tannins have been isolated from legume pasture species and purified by gel chromatography on Sephadex G-50 and LH-20 media. Molecular size di     

Stomach capacity as a directing factor in prey size selection of three-spined stickleback

Three-spined stickleback consumed prey of one size until the stomach was full whereafter similar-sized prey were rejected, but smaller prey were consumed. This evidence leads to the prediction of a shift in prey size preference as a result of the constraint imposed by remaining stomach capacity.     

Eye drop delivery of nano-polymeric micelle formulated genes with cornea-specific promoters

BACKGROUND: This study evaluates the eye drop delivery of genes with cornea-specific promoters, i.e., keratin 12 (K12) and keratocan (Kera3.2) promoters, by non-ionic poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) (PEO-PPO-PEO) polymeric micelles (PM) to mouse and rabbit eyes, and investigates the underlying mechanisms. METHODS: Three PM-formulated plasmids (pCMV-Lac Z, pK12-Lac Z and pKera3.2-Lac Z) containing the Lac Z gene for beta-galactosidase (beta-Gal) whose expression was driven by the promoter of either the cytomegalovirus early gene, the keratin 12 gene or the keratocan gene, were characterized by critical micelle concentration (CMC), dynamic light scattering (DLS), and atomic force microscopy (AFM). Transgene expression in ocular tissue after gene delivery was analyzed by 5-bromo-4-chloro-3-indolyl-beta-D-galactoside (X-Gal) color staining, 1,2-dioxetane beta-Gal enzymatic activity measurement, and real-time polymerase chain reaction (PCR) analysis. The delivery mechanisms of plasmid-PM on mouse and rabbit corneas were evaluated by EDTA and RGD (arginine-glycine-aspartic acid) peptide. RESULTS: The sizes of the three plasmid-PM complexes were around 150-200 nm with unimodal distribution. Enhanced stability was found for three plasmid-PM formulations after DNase I treatment. After six doses of eye drop delivery of pK12-Lac Z-PM three times a day, beta-Gal activity was significantly increased in both mouse and rabbit corneas. Stroma-specific Lac Z expression was only found in pKera3.2-Lac Z-PM-treated animals with pretreatment by 5 mM EDTA, an opener of junctions. Lac Z gene expression in both pK12-Lac Z-PM and pKera3.2-Lac Z-PM delivery groups was decreased by RGD peptide pretreatment. CONCLUSIONS: Cornea epithelium- and stroma-specific gene expression could be achieved using cornea-specific promoters of keratin 12 and keratocan genes, and the gene was delivered with PM formulation through non-invasive, eye drop in mice and rabbits. The transfection mechanism of plasmid-PM may involve endocytosis and particle size dependent paracellular transport.     

Sex-specific niche partitioning and sexual size dimorphism in Australian pythons (Morelia spilota imbricata)

Sexual dimorphism is usually interpreted in terms of reproductive adaptations, but the degree of sex divergence also may be affected by sex-based niche partitioning. In gape-limited animals like snakes, the degree of sexual dimorphism in body size (SSD) or relative head size can determine the size spectrum of ingestible prey for each sex. Our studies of one mainland and four insular Western Australian populations of carpet pythons ( Morelia spilota ) reveal remarkable geographical variation in SSD, associated with differences in prey resources available to the snakes. In all five populations, females grew larger than males and had larger heads relative to body length. However, the populations differed in mean body sizes and relative head sizes, as well as in the degree of sexual dimorphism in these traits. Adult males and females also diverged strongly in dietary composition: males consumed small prey (lizards, mice and small birds), while females took larger mammals such as possums and wallabies. Geographic differences in the availability of large mammalian prey were linked to differences in mean adult body sizes of females (the larger sex) and thus contributed to sex-based resource partitioning. For example, in one population adult male snakes ate mice and adult females ate wallabies; in another, birds and lizards were important prey types for both sexes. Thus, the high degree of geographical variation among python populations in sexually dimorphic aspects of body size and shape plausibly results from geographical variation in prey availability.  © 2002 The Linnean Society of London, Biological Journal of the Linnean Society , 2002, 77 , 113–125.     

Impact of climatic variation on populations of pine processionary moth Thaumetopoea pityocampa in a core area of its distribution

• 1 There is growing appreciation of climatic effects on insect population dynamics at the margins of distribution limits. Climatic effects might be less important and/or involve different drivers and processes near the centre of distributions.
• 2 We evaluated the effects of interannual variation in temperatures, radiation and precipitation on populations of pine processionary moth Thaumetopoea pityocampa in Central–South Portugal, a low altitude area with a relatively mild Mediterranean climate near the centre of the north–south range of the species.
• 3 We tested for effects of climate on mortality of young larvae, growth rates, final larval mass and fecundity.
• 4 Results indicated high mortality of early instars associated with low minimum and maximum daily temperatures and low precipitation. Low minimum temperatures were further associated with high parasitism by the larval parasitoid Phryxe caudata (Rondani) (Diptera, Tachinidae). Furthermore, larval growth rates were higher with high solar radiation during December and January, which was itself negatively related to precipitation and air temperature. Slow larval growth rates led to lower final mass at pupation in the spring, and smaller egg masses and smaller initial colony sizes during the next autumn.
• 5 Thus climatic factors, and temperature in particular, apparently contributed to population dynamics of T. pityocampa in the core of its distribution, as well as at its northern limits. The most specific climatic parameters of importance, however, and the connections between climate, physiology and insect demographics in the core area were clearly different from northern areas.